An Evaluation of Short-Term Forecasts of Wintertime Boundary-Layer and Surface Energy Budget Statistics in the Central Arctic

This presentation uses observations taken during the MOSAiC campaign to evaluate the simulation of wintertime statistics of the central Arctic near-surface atmosphere and surface energy budget in short-term forecasts from seven state-of-the-art operational and experimental forecast systems. Five of these systems are fully-coupled ocean-sea ice-atmosphere models. Forecast systems need to simultaneously simulate the impact of radiative effects, turbulence, and precipitation processes on the surface energy budget and near-surface atmospheric conditions in order to produce meaningful forecasts of the Arctic system. The focus is on processes unique to the Arctic, such as, the representation of liquid-bearing clouds at cold temperatures and the representation of a persistent stable boundary layer. It is found that contemporary models still struggle to maintain liquid water in clouds at cold temperatures. Only two models simulate the observed distinct bi-modal clear-sky and cloudy modes that are characteristic of Arctic surface radiation. One of these models has cloud liquid similar to observations and the other produces enough cloud ice without cloud liquid to produce the two distinct modes. Three of the models have distinct clear-sky modes but underestimate the cloudy mode. Two of these models are the only models that produce the observed decrease in turbulent heat flux for strongly stable near-surface conditions. Using a diagnostic that displays all three terms of the surface energy budget, it is seen that these three models have variability in regimes with few observed occurrences; clear-skies with large upward conductive surface flux and small sensible heat flux, and large downward sensible heat flux and small conductive surface flux. This study demonstrates that evaluating simulations from a coupled perspective provides new insight into model biases of the Arctic system.